AbstractEinstein metrics can be characterised as critical points of the (normalised) total scalar curvature functional. They are always saddle points. However, there are Einstein metrics which are local maxima of the functional restricted to metrics of fixed volume and constant scalar curvature. These are by definition stable Einstein metrics. Stability can equivalently be characterised by a sp...
AbstractRecent years have witnessed an explosion of studies of the non-invertible symmetries in various dimensions. In this talk, I will revisit the most vanilla type of non-invertible symmetry — Kramers-Wannier duality symmetry in (1+1)d, from three different perspectives: 1. lattice; 2. field theory; 3. Symmetry TFT. I will explain the construction of non-invertible defects, their fusion rul...